Ship&#39;s davit



Nov. 24, 1931. J. 5. BARCLAY SHIPS DAVIT Filed Oct. 9, 1929 I] I "In.

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Patented Nov. 24, 1931 UNITED STA TES 301m SYDNEY BARCLAY, or LONDON, ENGLAND snrrs DAVIT Application filed Octo ber 9,1929, Serial No. 398,368, and in Great Britain October 15, 1928. g

, This invention is forimprovements inor relating to ships davits of the kind known as gravity davits, in which a davit has a bodilyinboard and outboard movement on the davit frame, with or without a turning move-' davit-frame, and thence over another pulley at or near the head of the davit to the boat. According to another feature of this in vention, the arrangement of the falls is further characterized in that the run of the; fall to the first-mentioned pulley lies substantial- 1y along the path of the inboard and outboard movement of the davit.

This invention alsocomprises a davit as above described, wherein the above-mentioned pulley on the davit is so positioned that when the davit is in its out-turned position the loading on the pulley, due to the ten sion in the falls, assists in turning the davit towards its inboard position.

In one form of this invention, it is applied to a gravity davit of the type in which the davit proper is supported at two points by rollers each engaging a track along which the rollers travel inthe same or similar paths, and this invention comprises a gravity davit of this type wherein the outboard turning movement of the davit takes place towards the end of its travel on thetrack, by a turning movement about one roller as a centre, the other roller being separated from its guiding track during each turning movement.

' of it and the novel details thereof pointed out Other features of this invention will be de scribed in relation to a specific embodiment in the claims.

' The accompanyingdrawing is a diagrammatic view showing inside elevation one con-' struction of davit in accordance With the present invention.

Referring to the accompanying drawing, the deck of a ship is indicated at 1 and the side of the ship at 2. Adavit-frame com prises a vertical portion 3 at the side of the ship and a 19011710114 sloping upwards and inwards, this portion being supported at its inner end 5 upon a stanchion 6 or upon the roof of a deck-house or in any other convenient manner. The sloping portion 4 constitutes a guide or track whereon the davit proper, which is indicated ,generally'by the reference 7, can move in an inboard or out, board direction. As illustrated, the davit 7 comprises an extended base portion 8 and an The davit 7 can be traversed along the frame-member 4 and is guided by the rollers 11, 12 in the track. If the track 4 is curved at its outer end, an outboard turning move ment will be imparted to the davit 7 thereby, but it is preferred to effect the outboard turning movement by a pivotal movement of the davit about the roller 11. For this purpose a 7 gap 18 is provided in the upper wall of the channel 4 at a position such that the roller12 is oppositeto it when the roller 11 is at or near the limit of its movement in the track 4, so that the roller12 can be carried out to the position indicated in chain-lines inthe outboard position of the davit 7 r i A further guide is provided for this'outboard turning movement by means of a roller 14 mounted on the base 8 of the davit 7, so that it normally lies above the frame-member 4, and rides off the end thereof when the davit reaches the end of its outboard travel along that member. A guide block 15 is secured on the end of the member 4, this being curved to the arc of a circle about the centre of the roller 11 when it is in the position in which the swinging movement takes place.

When the davit 7 is in its out-turned position, the lower end or heel of the base 8 swings into a position adjacent the upright frame-member 3, and there may be provided on this frameanember a stop 16. If desired, this may be of rubber or of other yielding or resilient construction in order to reduce any shock which may occur during the outward swinging movement of the davit.

The fall for this davit is arranged in the following manner. Starting from the winch 17, which is situated in any convenient position, the fall is led around such guide-pulleys as may benecessary, to a guide-pulley 18 situated at the upper end of the sloping portion of the'frame-member 1, and it passes thence downwards to and around a pulley 19 secured on the davit 7, and thence back to another guide-pulley 20 which, conveniently, is coaxial with the pulley18 aforesaid. For clearness in illustration the pulley 20 is shown as smaller than the pulley 18, butthese would. of course, be the same size in practice.

The falls are then led upwards over such guide-pulleys 21 as may be necessary, to a pulley'22 at the head of the davit 7, and the end of thefall beyond this pulley is engaged with the boat 23.

Upon the head of the davit 7 there is provided a hook-shaped member 24 which, as is usual with gravity davits, is adapted to he engaged by a cross-pin 25- on the falls so that the weight of the boat-can be taken wholly or in part directly on the davit-head instead of solely on the falls. The hook is shaped so that it is engaged automatically by the pin 25 as the boat is raised.

The pulley 19 might be situatedcoaxially with the roller 11, but, preferably, it is in such a position that when the davit is in its out-' turned position, as shown inchain-lines, the pulley is situated somewhat above the roller 11 so that the tension in the two runs of the falls which engage the pulley 19 tends to rotate the davit 7 about the roller 11; furthermore, the position is so selected that when the davit 7 is in its inturned position, the runs of the fall engaging the pulley 19 are substantially aligned with the track 4 along which the davit moves.

The operation of this device is as follows: Assuming that the davit is in its normal inboard position, and it is desired to lower the boat, the only operation necessary is that the winch should be released, and allowed to run out under the control of a suitable brake. The first action is that the davit 7 runs down the track .4, and during this movement the arrangement of pulleys 18, 19, 20., 22 gives a triple purchase with a velocity ratio of nearly 3 to 1 so that the movement of the slow compared with the rate of move ment of the winch. When the davit approaches the end of its outboard travel, and the roller 12 comes opposite the gap 13 aforesaid in the guide, the davit is free to turn outwards. Such movement, however, is controlled by the falls, since the pulley 19 on the davit still continues to move, and thereby continues to provide substantially a triple purchase control. When the limit of the turning movement is reached, the pulley 19 becomes stationary and further movement of the winch effects-the lowering of the boat by a single purchase gear. The turning movement of the davit has released the pin 25 from the hoolc2 l, as is shownin chain-lines, and the boat is free to be lowered.

It is to be understood that the free end of the fall beyond the pulley 22 need not be directly connected to the boat, for any multiplying gear can be used if desired for'large boats, in such cases it will be clear that the single and triple purchase above-mentioned refers to the tension in the fall at the pulley 22 and the force acting on the davit.

An important advantage of this invention is that when the falls are loaded,.that is to say, when supporting a boat, the tension in the various runs of the falls engaging the pulleys on the davit, is such that the total force acting on'the davit is in an inboard direction. Thus, the resultant forces on the two pulleys 21, 22 when in the outboard position are both directed downwardly and inwardly; the pulley 19 is subjected to two tensions both directed inwards, and more or less aligned with the frame-member 4;. It follows, therefore, that the frame-members are not subjectedto the stresses which would be required to support the .davit as a cantilever when the load of the boat is on it, and in fact, the greatest stress to which the frame is subjected is that due merely to the weight of the davit and boat. This characteristic of the present invention is particularly advantageous insofaras it facilitates the mounting of the davits on the ship-structure without requiring as much reinforcement of the ships structure as has hitherto been necessary with davits.

The .reverse operation of hoisting a boat will be clear from the foregoing description. The boat is lifted from the Water to the davithead by a single purchase gear and when the pin 25 aforesaid engages the davit-head, the inboard turning movement of the davit7commences. This turning movement is effected partly by the tension in the run of the fall engaging the pulleys 21, 22, and it is assisted by the tensions in the runs of the fall engaging the pulley 19. This movement is eifected by What is substantially a triple purchase gear, and when the turning movement is con1- plete the davit is hauled up the frame 4: also by a triple purchase gear. It will be seen, therefore, that both in lowering and raising a boat the relatively slow movement obtained by triple purchase gear as contrasted with a single purchase gear is available during the particular periods at which it is desired, namely, during the outboard travel of the davit and the outboard turning movement. Thereafter the direct lowering of the boat which can safely be effected at a higher speed is obtained by a single purchase gear.

I claim 1. In a ships davit the combination with a supporting-frame having a track which slopes upwards and inwards from the side of the ship, of a davit-arm which is supported at two points by rollers movable along said track in similar paths, said arm being capable of turning about one roller ascentre when moved towards the outboard end of the track, said other roller being separated from said track during such turning movement.

, 2. In a ships davit the combination with a supporting frame having a track of channel section which slopes upwards and inwards from the side of the ship, of a davit-arm which is supported at two points by rollers movable along said track in similar paths, J said arm being capable of turning about one roller as centre when moved towards the outboard end of the track, said track having a gap therein to permit the other of said rollers to be disengaged therefrom during such turning movement.

3. In a ships davit the combination with a supporting-frame having a track of channel section which slopes upwards and inwards from the side of the ship, of a davit-arm which is supported at two points by rollers movable along said track in similar paths, said arm being capable of turning about one roller as centre when moved towards the outboard end of the track, said track having a gap therein to permit the other of said rollers to be dis engaged therefrom during such turning movement, and an additional roller co-operating with a guide-member on the track which becomes operative during the turning movement of the davit.

4. In a ships davit, the combination with a supporting-frame having a track which slopes upwards and inwards from the side of the ship, of a davit-arm which is supported on said track and is movable therealong to an outboard position, a winding mechanism (e. g. a winch), a plurality of sheaves and a fall for varying the position of the davit-arm and the boat, which fall is reeved around'a sheave mounted near the base of said arm, thence to a sheave on the supporting-frame and thence to a sheave mounted near the head of said arm and to the boat, the sheave near the base of the said arm'and the sheave on the said supporting frame being in such a relation to one another that whilst the said davit arm is moving along the said track the fall has a two part purchase on said davit arm.

5. In a ships davit, the combination with a supporting-frame having a track which slopes upwards and inwards from the side fof the ship, of a davit-arm which is sup- .portedon said track and is movable therealong to an outboard position, a winding mechanism, a fall for varying the position of the davit-arm and the boat, which fall is led from said Winding mechanism substantially along the path of the inboard and outboard movement of the davit-arm to a sheave mounted at the base of said arm, thence to a sheave on the supporting-frame and thence to a sheave mounted near the head of said arm and to the boat, the sheave near the base of the said arm and the sheave on the said sup-.1

porting frame being in such a relation to one another that whilst the said davit arm is moving, along the said track the fall has a two part purchase on said davit arm.

6. In a ships davit the combination with a supporting-frame having a track which slopes upwards and inwards from the side of the ship, of a davit armwhich is supported at two points by rollers movable along said track in similar paths, said arm being cav pable ofturning about one roller as centre when moved towards the outboard end of the track, said other roller being separated from said track during such turning movement, a winding mechanism (e. g. awinch), a plurality of sheaves, and a fall for varying the position of the davit-arm and the boat, which fall is reeved around a sheave mounted near thebase of said arm, thence to a sheave on the supporting-frame and thence to a from the side of the ship, of a davit-arm which is supported at two points by rollers movable along said track in similar paths,

said arm being capable of turning about one roller as centre when moved towards the outboard end of the track, said trackv having a gap therein to permit the other of said rollers to be disengaged therefrom during such turning movement, a winding mechanism (e. g. a winch) a plurality of sheaves, and a fall for varying the position of the davit-arm and the boat, which fall is reeved around a sheave mounted near the base of said arm, thence to a sheave on the supporting-frame and thence to a sheave mounted near the head of said sheave mounted near the base of said arm,

thenceto a sheave on the supporting frame "and thence to a sheave mounted near the head "of said'arrn and to the boat, the sheaves near the base of the said arm on said supporting frame and near the head of said arm having the fall reeved around them in such a manner that whilst the said arm is moving "alon the track from the inboard to the outboard position the fall has a two part purchase on said arm which gradually merges into a substantially three part purchase, and when the arm is in its outboard position the fall acts 1ljay "single purchase to raise and lower the oat.

9. In a ships davit, the combination with a supporting frame having a track which slopes upwards and inwards from the side of the ship, of a davit arm which is supported on said track and is movable therealong to an outboard positioma winding mechanism, a fall for varying the position of the davit arm and the boat, which fall is led from said winding mechanism substantially along the path of the inboard and outboard movement of the davit-arm to a sheave mounted at the base of said arm, thence to a sheave on the supporting frame and thence to a sheave mounted near the head of said arm andto the boat, the sheaves near the base of the said arm, on said supporting frame and near the head of said arm having the fall reeved around them in such a manner that Whilst the said arm is moving along the track from the inboard to the outboard position the fall has a two part purchase on said arm, which gradually merges into a substantially three part purchase on the said arm, whilst when the arm is being moved from the outboard position to the inboard position the substantially three part purchase gradually merges into'a two part purchase of the fall, and when ith'e arm is in its outboard position the fall illets by single purchase to raise and lower the oat.

In testimony whereof I afiix my signature.

JOHN SYDNEY BARCLAY. 

